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Surprise Top Hat 


Make Projects 

build, hack, tweak, share, discover. 

Surprise Top Hat 

Written By: Dug North 


Drill (1) 

Hobby knifed) 
Hot glue gun (1) 
Jigsaw (1) 
Pliers (1) 
Scissors (1) 
Screwdriver (1) 


Plywood (1) 

Screw eye (1) 

Epoxy (1) 

Hinges (1) 

Metal L brackets (1) 

Springs (2) 

length will depend on your hat 

Bicycle brake system (1) 

PVC pipe (5" length) 

Costume coachman's hats (2) 

Ribbon (1) 

Finger puppet (1) 

Screws (1) 

Aluminum cable sleeve (1) 

for making a loop at the end of a cable 


I routinely wear a derby hat around town. So when the Halloween season approaches, I feel 
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Surprise Top Hat 

the need to wear a hat that really makes a statement. I decided to combine my fondness for 
old-style hats with my love of mechanical automata. The result is this trick top hat. A little 
monster hides insides the hat and springs out of the top whenever I squeeze a hidden hand 

Step 1 — Prepare the hat. 

• To create a hat that's tall enough to 
house the mechanism, combine 2 
costume top hats -- sold as 
"coachman's hats" -- into one large 
hat. Cut the top off one hat. This 
will serve as the base hat, which 
will sit on your head and hold the 
mechanism base. 

• Cut the top and brim off the second 
hat. Later, this tubular piece will 
form the upper half of the hat. Save 
all the pieces. 

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Surprise Top Hat 

Step 2 — Build the framework. 

• You'll mount the pop-up mechanism to an oval plywood base fitted within the top rim of the 
base hat. Cut a plywood oval to fit the base hat. 

• To support the pivoting parts, mount a plywood rectangle upright, perpendicular to the 
base, with metal L brackets. 

• Cut a slot most of the way down the middle of the upright support, to create clearance for 
the moving parts. 

• Screw an additional piece of wood to the back of the support -- just to one side of the slot - 
- to provide a place to screw the pivoting parts to the mechanism base. 

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Surprise Top Hat 

Step 3 — Make the pop-up mechanism. 

• The mechanism is a 4-bar linkage-a wooden parallelogram with 2 horizontal and 2 vertical 

• There are 2 fixed pivot points at the rear of the 4-bar linkage, and 2 swinging ones in the 
front. The 4-bar linkage amplifies a short pull from the cable into a larger upward motion of 
the front-most vertical bar. 

• Fit the rubber finger puppet over the top of the front-most bar of the linkage. Attach a 
spring to the base and the front bar, to pull the monster back into the hat when the hand 
lever is released. 

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Surprise Top Hat 

Step 4 — Wire it up. 

• Mount the brake lever to your 5" PVC handle, then attach the appropriate end of a 
universal brake cable to the brake lever. 

• Cut the opposite end of the cable off, leaving the cable housing and metal ferrule intact. 

• Countersink a hole halfway through the underside of the oval plywood base, directly below 
the end of the linkage bar that the cable will pull; this pocket hole will accept the cable 

• Drill a smaller hole completely through the center of the first hole, to allow the cable itself 
to pass through the base. 

• Epoxy the metal ferrule to the base, and thread the cable through the smaller hole. 

• Pass the cable through a hole drilled in the end of the lowest linkage bar. 

• Secure the loop formed by the doubled-over cable with an aluminum cable sleeve. 

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Surprise Top Hat 

Step 5 — Finish the hat. 

• Attach the mechanism base to the base hat with small screws. 

• To hide the mechanism, invert what remains of the second hat and glue it to the base hat 
with hot glue. Hide the seam with ribbon, applied while the hot glue is still tacky. 

• Use the extra hat pieces to create a hinged lid. The hinges are mounted to the top of the 
upright support. 

• When the hand level is actuated, the upper horizontal bar of the 4-bar linkage lifts the 
hinged lid out of the way of the ascending monster. 

• Another spring between the base and the lid ensures that it closes after the monster 

• To operate, wear the hat and run the cable down the sleeve of a coat. 

• Squeeze the brake lever and ... surprise! 

This project first appeared in Make: Halloween Special Edition , page 54. 

This document was last generated on 2012-11-03 02:52:34 AM. 

© Make Projects 

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